Methanolysis for PET Bottle Recycling

Improved process for depolymerizing polyethylene terephthalate (PET) using an electrolysis cell to produce a specific type of solvent called methanolic sodium methylate. This solvent is used in the depolymerization reaction to break down PET into bis (2-hydroxyethyl) terephthalate (BHET) at high yield with low by-products compared to traditional methods. The process involves electrolyzing methanol and sodium hydroxide to create the solvent, which is then used in the PET depolymerization step. The electrolysis cell design and separator construction are optimized to prevent solvent leakage during the process.

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Recycling PET-based materials like disposable bottles, trays, fabrics, and insulation into terephthalate esters like dimethyl terephthalate (DMT) using a simple, room temperature process without pre-treatment. The method involves grinding the PET waste into chips, then reacting it with an alcohol like methanol or ethanol at atmospheric pressure and room temperature for less than an hour. The PET breaks down into terephthalate esters and the alcohol. This allows recycling of contaminated PET materials like fabrics with elastane or cotton blends.

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Magnetic solid alkali catalyst for efficient methanolysis of polyester materials like PET to produce pure dimethyl terephthalate (DMT) without distillation. The catalyst is a composite oxide derived from roasting magnesia or magnesium aluminum iron hydrotalcite at 400-600°C. It allows high yield DMT production at lower temperatures and shorter times compared to conventional catalysts. The catalyst separates easily from the reaction mixture. This simplifies product separation and reduces energy consumption compared to distillation.

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A process for recycling PET plastic waste into terephthalate ester monomers, like dimethyl terephthalate (DMT), without any pretreatment steps and in less than an hour. The process involves two stages: (1) depolymerization of PET by methanolysis using an alcohol like methanol and an ester catalyst like titanium ethoxide; (2) separating and purifying the DMT from the reaction mixture. The mild conditions and catalyst selection prevent isomerization or degradation reactions.

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A process to efficiently depolymerize polyethylene terephthalate (PET) into dimethyl terephthalate (DMT) and monoethylene glycol (MEG) using catalytic amounts of sodium methoxide. The process involves breaking down PET back into its starting materials by reacting it with methanol in the presence of sodium methoxide as a catalyst. The resulting DMT and MEG can then be separated and purified for use in various applications. The process allows for selective depolymerization of PET into its monomers in high yields and with low impurity levels.

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A process for recycling PET plastic waste into dimethyl terephthalate (DMT) monomer powder in a few hours by using mild reaction conditions. The process involves three stages: (1) pretreating the PET fragments to facilitate depolymerization, (2) reacting the pretreated fragments with methanol in the presence of catalytic amounts of bases like sodium methoxide, DBU, or potassium hydroxide, and (3) heating for 3-5 hours at 25-80°C. The mild conditions prevent isomerization or degradation of the DMT, allowing a complete reaction without the need for extensive purification.

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Recycling polyester waste into usable chemicals like dimethyl terephthalate (DMT) and cyclic carbonates by depolymerizing the polyester with methanol. The process involves depolymerizing the polyester in a reactor to form DMT and diol, then converting the diol into a form that won't react with DMT. This prevents DMT loss during further processing. The diol conversion step can be done in the same reactor as depolymerization. The diol conversion can be using compounds like cyclic carbonate precursors, allowing in-situ formation of cyclic carbonates. This avoids separating out DMT and diol for separate reactions.

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Recycling of polyester waste by depolymerization using methanolysis, followed by selective hydrogenation of side products to improve the quality and utility of the resulting stream. The method involves depolymerizing polyester waste using methanol to obtain dimethyl terephthalate (DMT) along with side products like dimethyl phthalate (DMP), dimethyl isophthalate (DMI), bisphenol A (BPA), adipic acid diester, and colorants. The DMT is hydrogenated to produce 1,4-cyclohexanedicarboxylate (CHDC) or 1,4-cyclohexanedimethanol (CHDM). Side products like DMP and BPA are also hydrogenated. This converts them into more valuable chemicals while also removing impurities that can negatively impact recycling

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Catalysts for methanolysis of poly(ethylene terephthalate) (PET) to form dimethyl terephthalate (DMT) that provide improved performance compared to conventional catalysts like zinc acetate. The new catalysts, such as sodium carbonate, magnesium methoxide, 1,8-diazabicyclo[5.4.0]undec-7-ene, and triazabicyclodecene, allow methanolysis of PET at lower temperatures and with less methanol than zinc acetate. They also tolerate lower quality PET waste feeds.

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Catalysts for methanolysis of poly(ethylene terephthalate) (PET) that provide improved depolymerization efficiency compared to the traditional zinc acetate catalyst. The new catalysts include sodium carbonate, magnesium methoxide, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and triazabicyclodecene (TBD) which allow PET depolymerization at lower temperatures and with less methanol compared to zinc acetate. This reduces energy consumption and cost for recycling PET waste.

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Method for recycling waste polyester into new polyester using alcohol decomposition followed by transesterification. The method involves melting the waste polyester, adding ethylene glycol for pre-alcohol decomposition, then decomposing the melted polyester in an alcohol solvent with a catalyst. This step yields a transesterification product. Next, transesterification is performed in a separate kettle using the transesterification product, ethylene glycol, and catalyst to produce dimethyl terephthalate (DMT) and ethylene glycol. The purified DMT is recycled for polyester production.

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Efficient and economical process for recycling PET plastic waste into dimethyl terephthalate (DMT) and monoethylene glycol (MEG) for reuse in new PET production. The process involves depolymerizing PET using methanol and sodium methoxide at controlled ratios and temperatures. The key steps are: (i) adding sodium methoxide to PET waste, (ii) adding methanol in multiple fractions, (iii) heating to depolymerize, and (iv) separating DMT and MEG. This allows selective degradation of PET into the desired products with high yields. The optimized conditions are: 1:5-1:20 mol/mol sodium methoxide:PET, 0.2-3.0% mol/mol sodium methoxide in

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A process for efficiently depolymerizing recycled polyethylene terephthalate (PET) into dimethyl terephthalate (DMT) and monoethylene glycol (MEG) using methanol and sodium methoxide. The process involves swelling the PET with methanol before adding sodium methoxide to initiate depolymerization. Methanol is consumed during depolymerization, and additional methanol is added to maintain sodium methoxide levels. This allows high DMT and MEG yields. The swelling step improves mass transfer and reaction rates. The process can recycle PET with contaminants like other polymers, paper, and dyes.

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A process for recycling polyester that involves depolymerizing the polyester using methanolysis, hydrogenating the resulting dimethyl terephthalate to cyclohexanedicarboxylate and cyclohexanedimethanol, and hydrogenating the side species like dimethyl phthalate, bisphenol A, and adipic acid diester. This converts undesirable side products into more valuable compounds that can be isolated. The hydrogenation and isolation steps improve the overall quality and commercial value of the recycled polyester stream.

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A method for depolymerizing polyesters using methanolysis that increases polyester depolymerization and reduces methanol requirements. The method involves treating the polyester with methanol in a reactor to form dimethyl terephthalate and diols. Some of the diols are then converted to non-reactive compounds like cyclic carbonates. This allows the diols to react further without interfering with the dimethyl terephthalate. The non-reactive compounds are separated from the dimethyl terephthalate to prevent further reactions. This prevents excessive methanol usage compared to traditional methanolysis where all diols react with methanol.

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Recycling polyester waste to produce useful chemicals while minimizing environmental impact. The method involves treating the product stream from polyester depolymerization by methanolysis to convert side species like dimethyl phthalate, dimethyl isophthalate, bisphenol-A, adipic acid diester, and colorants into valuable compounds. This is done by hydrogenating the side species along with the dimethyl terephthalate. The hydrogenated side species can then be isolated and further processed or disposed of more easily. This allows converting unwanted side products into valuable chemicals instead of disposing them, reducing waste.

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Continuous method for recycling waste polyester into dimethyl terephthalate (DMT) using alcohol decomposition and transesterification. The method involves drying and deoxygenating the waste polyester to prevent side reactions. The dried polyester, alcohol, and catalyst are continuously fed into a first alcohol decomposition reactor. The product is further decomposed in a second reactor. The alcohol-decomposed material is then subjected to transesterification with more alcohol and catalyst to yield crude DMT. Crystallization, separation, and purification completes the recycling process.

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Continuous process for recovering waste polyester like PET bottles and converting it into usable chemical feedstock like dimethyl terephthalate (DMT) for making new polyesters. The process involves two steps: continuous alcoholysis of waste polyester using ethylene glycol (EG) followed by continuous transesterification using methanol. The alcoholysis is done in two stages to remove excess EG. This allows high DMT yield and quality without distillation or concentration. The transesterification is done in two stages to improve conversion. The process starts with drying and deoxygenating the waste polyester to remove moisture and oxygen.

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A method for degrading waste polyester like polyethylene terephthalate (PET) into dimethyl terephthalate (DMT) with high efficiency and low equipment requirements. The method involves two-step alcoholysis using glycols followed by methanol transesterification. In the first step, preliminary alcoholysis at 150-190°C converts PET into a slurry with 20-60% depolymerization. This slurry is then subjected to deep alcoholysis/methanol transesterification at 190-200°C. The mixture of glycols and methanol promotes PET depolymerization and moves the alcoholysis equilibrium forward. This accelerates both steps and improves material utilization compared to separate alcoholysis and methanol transesterification.

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Efficient and cost-effective process for recycling polyethylene terephthalate (PET) into dimethyl terephthalate (DMT) and monoethylene glycol (MEG) using sequential addition of methanol and sodium methoxide. The process involves mixing PET with a first portion of methanol to swell the PET, followed by addition of sodium methoxide. Additional methanol is then added in fractions over time to depolymerize the PET into DMT and MEG. This sequential methanol addition helps control the reaction conditions and prevents excessive methanol consumption.

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